1. Field of the Invention
The present invention relates to using a supercritical fluid, typically water, with or without additives such as inorganic salts, selected hydrocarbons, or other soluble elements or compounds such as oxygen, air, carbon monoxide or carbon dioxide to successfully refine hydrocarbons, such as heavy oil, bitumen and bitumen-like hydrocarbons. Heavy oil is a hydrocarbon with API gravity lower than 20° often containing sulfur compounds and associated heavy metals that are removed as part of the upgrading process. Bitumen or bitumen-like is defined as any hydrocarbon with a viscosity greater than 1000 cp at standard temperature and pressure. Supercritical fluids or fluid mixtures, typically water extracts the heavy oil/bitumen from a solid then thermally split the higher molecular weight hydrocarbons into lighter, more volatile hydrocarbons of higher value. The reaction portion of the method delivers the lighter weight, volatile hydrocarbons to a multi-phase contacting device that uses a thermal gradient to separate the hydrocarbon mixture into portions that are viable for use or sale without further refining.
2. Description of the Prior Art
World oil supply is changing and the readily available medium to light crude oil reserves are getting harder to find and develop. Since the world energy demand is increasing, particularly in emerging economies such as India and China, heavier oil reserves will be necessary to meet the demand as an alternative to more exploration and developing conventional oil reserves. Recovery and field development techniques for unconventional reserves have been progressing, such as steam assisted gravity drainage (SAGD), but current refining technology is based on combinations of feed de-salting, high-vacuum distillation, and then conventional hydrocracking or a combination of coking, thermal cracking followed by some form of hydro-processing using various catalysts and process gases. This requires complex, expensive equipment and an involved refinery infrastructure that includes capacity to produce hydrogen, heating fuel and maintain equipment and supplies. The conventional approach also generates large amounts of carbon dioxide from the heating required to drive the main distillation column, associated upstream, and downstream processing. The inventor believes that the concept presented here can produce similar products with fewer processing steps and therefore lower costs, increase worker safety due to fewer process steps and less reagent handling, allow greater opportunity for new oil field development and subsequent positive economic impact, reduce the amount of carbon dioxide, and associated waste products typically associated with conventional refineries.
U.S. Pat. No. 3,989,618 discloses a process for upgrading a hydrocarbon fraction by contacting the hydrocarbons with a supercritical water over a temperature range of 600° F. to 900° F. with no catalyst of added hydrogen. However, other additives are an important part of the process as the description goes on to add that it is useful to add a biphenyl, pyridine, a partly hydrogenated aromatic oil, or a mono- or polyhydric compound such as methanol to the water to add in the hydrocarbon upgrading process. The process as described can be carried out in a batch, semi-continuous or continuous fashion requiring minutes up to six hours of contact for satisfactory removal of sulfur, various metallic compounds and producing lighter hydrocarbon compounds.
The method is limited by mentioning that using carcinogens such as aromatic hydrocarbons aids the reaction process even though the process does not require a typical ‘cracking’ catalyst or added hydrogen. The aromatic hydrocarbons provide an in-situ source of hydrogen with the penalty of having to add reagents to allow operation at lower temperatures and pressures. In addition, the process does not provide a method for how to handle the unreacted portion of the feed or a means to control the reaction so that the product distribution can be controlled.
U.S. Pat. No. 4,818,370 discloses a process for upgrading heavy oil in a subterranean reservoir using supercritical ‘brine’ in combination with in-situ combustion to provide heat. The ‘brine’ is salt water typically found in oil reservoirs. An oxidizing gas in injected into the reservoir to enable a combustion zone that heats the heavy oil to allow it to drain into the combustion zone which contains the brine and is heated and pressurized to supercritical conditions. After a suitable time, the heavy oil is converted to lighter components that are removed from the reservoir using conventional recovery methods.
The method is limited to working with heavy hydrocarbons in-situ and the efficiency of the said method is dependent on the reservoir conditions and physical properties. No method is described to provide control of the reaction conditions such as the rate, contact times, reagent ratios, temperature, or pressure. It would be difficult to ensure that optimal conditions are maintained to get the best product distribution. In addition, it requires additional means to inject oxidizing gases and recover the combustion gases that contribute to the carbon footprint of the process.
U.S. Patent Publication 2007/0056881 A1 discloses a method for upgrading heavy hydrocarbons and the like using a flow-through reactor to contact heavy hydrocarbons with water at temperatures ranging from 250° C. to 450° C. and pressures ranging from 500 psi to 3000 psi. Said method uses simple reactor with inlets ports for the water and the hydrocarbons into the reactor, and an outlet port that directs the water-oil mix to a cooler that cools the mixture and allows separation. Other conditions described are the residence times from 28 seconds to 10 minutes and the additional allowance to introduce carbon monoxide or selected inert gases such as nitrogen into the reactor.
The method does not describe means to control the product distribution or quality or means to deal with unreacted heavy hydrocarbons. It is known that any heavy oil or bitumen processing method produces coke or other refractory carbonaceous material that must be handled in some fashion. This invention does not describe a method for handling carbonaceous residues that can be deleterious to reactor operation.
U.S. Pat. No. 7,754,067 discloses a method for upgrading heavy hydrocarbons and the like using supercritical water, means for contacting the hydrocarbons and supercritical water in two separate heating stages. In the first zone, heavy hydrocarbons are mixed with supercritical water at pressures above 22.1 MPa at temperatures up to 775 K in the first heating zone, and then the second zone is heated either by an external source or by bleeding in oxygen to in-situ heat the fluid up to 870 K to 1075 K. The said device is also has a convoluted or multi-pass contacting device with a nozzle device to try to disperse the hydrocarbons into the supercritical water.
The method is limited by the formation of solid carbonaceous materials that necessitate the shutdown and clean out of the reactor. The multi-pass portion required to effect the necessary mixing also limits the means to effectively clean and maintain the contacting device. In addition, the heating profile described is complex and requires shortened heat-up times between the heating stages to reduce coke formation. This limits the operating time and potential throughput of the method.
U.S. Pat. No. 7,144,148 B2 discloses a method for upgrading heavy oil and the like using a supercritical solvating hydrocarbon and means for contacting the heavy oil and solvating solvent using a fluidized bed of hot solids. The heavy hydrocarbons are contacted with the supercritical solvating hydrocarbon in a first fluidized bed at temperatures at or below 538° C. with the solid particulates providing a method for heat transfer. After reaction, the lighter hydrocarbons are removed and the solids transported to a second bed to remove accumulated coke formation.
The method is limited by using a solvating hydrocarbon to essentially dissolve and then react with the heavy hydrocarbons. This necessitates a solvent removal and recycle step along with handling the solid particulates used to transfer heat to the reaction mixture. An additional solids removal step is required to prevent the solid particulates from affecting downstream processing.